The immotile cilia syndromes (ICS) are a genetically determined set of disorders characterized by dysmotility or immotility of the cilia in airway epithelial cells, spermatozoa and other ciliated cells of the body. Kartagener syndrome (KS) is a subgroup of ICS characterized by a classic triad of symptoms: situs inversus, bronchiectasis and chronic sinusitis. Ciliary immotility is caused by various ultrastructural defects of cilia, predominantly by a lack of dynein arms. The clinical consequences of KS include pronounced craniofacial manifestations. In 1994, we initiated a large-scale collaborative genetic epidemiology study of KS with Dr. Michal Witt of Poznan, Poland. Polish families with at least one child affected with KS are being recruited for this study. Coded DNA samples and research medical records are being sent to our laboratory for genotyping and statistical analyses using linkage and linkage disequilibrium approaches. We use microsatellite markers and fluorescence-based automated DNA fragment analysis hardware and software.We performed a genome scan and have followed up promising regions with very high density STR mapping. To date, over 83,000 genotypes have been assayed for this study. We have reported exclusion of a candidate region on chromosome 7 for KS families. We have now obtained strong evidence of linkage to chromosome 15 with a multipoint LOD score of 5.0. We also very recently discovered evidence of a possible microdeletion commonly occurring in KS families. Experiments are currently underway to replicate and verify this potentially critical discovery, which could greatly facilitate identification of the KS gene.